They’re not even the same currency at all, yet Steam or any other digital storefront decides to price a 80€ ($91) game the same as a $80 (69€) one when the conversions in reality are different to what the algorithm suggests. It’s reflected on Steam DB that Euro has a higher markup in comparison to US Dollar because of this, since I hear EU players nagging about paying 80€ at launch the same as US players don’t like paying $80.
Since the marginal cost of selling additional digital copies is zero, I’d hazard that it’s priced that way because Europeans will pay that much and companies like to get money